Abstract: In generating seismic waves in earth a generator having a generally elongate, tubular expandable and contractible outer wall portion closed at its upper and lower ends by rigid strength members having separate input and return pressure lines is placed in a well bore, a hydraulic coupling pressure is applied through the input line which causes the expandable wall portion to engage and remain coupled with and in direct contact with the earth wall in the well bore and hydraulic pressure impulses are then cycled through the input and return lines at pressures greater than the coupling pressure to cause further expansion of the expandable wall portion, thereby generating and radiating seismic waves in the earth upon application of each impulse while maintaining the hydraulic coupling pressure sufficient to effectively maintain the outer wall anchored to the wall of the bore hole. The coupling pressure should be sufficient to anchor and couple the transducer to the well bore without any additional anchoring.

Abstract: Methods and apparatus describedmaximize, within a predetermined frequency band, the continuous or near-continuous transmission of broadband acoustic power into a medium having a finite tensile strength such as water or earth. Such methods and apparatus also minimize, for a given broadband acoustic power level in a given frequency band, the negative dynamic pressure or stress excursion of an acoustic signal with respect to the average pressure or stress present in the absence of the signal. Such signals may be transmitted for geophysical exploration purposes. The signals place the medium alternately under compressive and tensile stresses with respect to some average stress, where the time duration of the application of the compressive stress is short compared with the time duration of the application of the tensile stress. The tensile stress does not exceed the tensile strength of the medium or its interfaces.

Abstract: Quasi periodic pulse trains are generated and swept in repetition frequency over an octave. Spectral harmonics of the pulse trains which prevent the trains from having a constant or "flat" power spectrum over a frequency range much greater than an octave are reduced or eliminated by adjusting the shape of the pulses in the trains. By means of selecting the timing of the pulses, other harmonics are reduced or preferentially augmented. The spectral energy of the signals which are generated during a transmission interval is of the type which possesses an autocorrelation function with a narrow main lobe and low side lobe levels which is especially suitable for echo location purposes such as in geophysical exploration in which seismograms are constructed by cross correlation of the signals which are transmitted with those which are received from the geological reflection surfaces.

Abstract: The invention relates to a device for propelling a liquid projectile to create a shock wave by implosion, said device comprising a cylinder containing two pistons, a reservoir of pressurized fluid acting on the pistons, a stop for stopping the piston, a perforated connecting piece to permit the escape of the propelled liquid and for connecting the cylinder with a return mechanism. The invention is applied to underwater oil prospecting.

Abstract: A system for controlling the force imparted to the ground by a seismic vibrator. A signal is generated which is related to the peak force imparted to the earth and the control signal amplitude is varied in response thereto to achieve the desired force magnitude.

Abstract: The seismic source consists of a tank for containing a volume of water. The tank is held in firm contact with the ground by suitable weighting means. The tank wall that contacts the ground is thinner than the other walls. The volume of water in the tank is pressurized to one to three atmospheres. An imploder is mounted in the tank, submerged in the water. When the imploder is fired, reducing the tank pressure abruptly, a negative pressure pulse is generated in the water. The negative pressure pulse is transmitted from the water, through the thin ground-contacting wall, to the ground, producing an acoustic pulse whose first motion is one of rarefaction.

Abstract: A system for porting of hydraulic fluid in a hydraulically driven seismic energy vibrator of the reciprocating mass type. A mass is reciprocated relative to an earth contacting frame which includes at least two hydraulic piston rods coacting with internal cylinders within the mass. The piston rods, of the type having double rod ends, each include a single axial bore therethrough in communication with respective opposite sides of the piston ring assemblies, and cross porting is effected between opposite ends of the mass cylinders.

Abstract: A high pressure seal is formed between a stationary piston and a reciprocating cylinder. The seal includes a sleeve which has an inner diameter dimensioned to permit the cylinder to slide freely over the piston rod, the sleeve being in rigid contact at one end to the cylinder and the other end to an end plate surrounding the piston and closing the end of the sleeve. A bleeder port communicates with the outer surface of the piston rod, through the piston rod, and terminates at a low pressure supply. Bleeder grooves are formed around the inner wall of the sleeve. A first bleeder groove is positioned in the inner wall of the sleeve at the mid-stroke position of the piston with second and third bleeder grooves positioned at each extreme position of the piston stroke in the inner wall of the sleeve. A plurality of pressure drop grooves is formed along the inner sleeve diameter such that the hydraulic fluid passing from the cylinder into the sleeve will gradually drop in pressure as it moves toward the end plate.

Abstract: Methods and apparatus for generating and transmitting seismic signals for the purpose of seismic exploration are disclosed. The signals are force pulses shaped to have a spectrum constrained to the range of frequencies which are necessary for penetration to desired depths within the earth and for resolution of the geological reflection surfaces therein. These pulses are provided in a non-repetitive or aperiodic train, constructed to produce a transmitted energy spectrum whose mean energy extends smoothly at a substantially constant level over the spectrum frequency range, notwithstanding that the repetition frequency of the pulses may be swept over a frequency band much narrower than the spectrum range. The transmitted spectrum can exhibit an auto-correlation function having a major lobe which is predominant over any side lobes, corresponding to a desired level of resolution of the geological reflection surfaces.

Abstract: The present invention relates to a seismic transducer for generating waves in an elastic medium and is particularly applicable to the generation of low frequency shear waves. The transducer is comprised of a mass member having more than one parallel hydraulic cylinder disposed therein, a piston member disposed in each cylinder, each piston member including a piston and a pair of oppositely extending rods, and a frame interconnecting the ends of the piston rods which frame has a base surface thereon for engaging a surface of the elastic medium in energy coupling relationship. A system of hydraulic fluid bleed-back ports associated with the piston members serve to aid lubrication and keep high pressures off of the rod end seals. The present construction permits total enclosure of the mass member and plural piston member assembly.

Abstract: A mud pulse transmitter is presented for transmitting information by prese pulses to the surface during the drilling of a borehole. A vortex valve is controlled by a fluidic feedback oscillator to generate the mud pulses. The oscillator frequency may be varied or the oscillator turned on and off by valves in the feedback paths of the oscillator, thereby permitting the transmission of information.

Abstract: Apparatus for supplying a large amount of air periodically at a controlled rate to the air cushion beneath an air-cushion vehicle as particularly employed for coupling of controlled frequency seismic energy into the earth. The apparatus consists of a vehicle body which includes a compressed air supply or input to a self-contained plenum chamber space for applying air pressure through a multi-port rotary valve thereafter to be directed into an air cushion formed between the vehicle and the earth surface with periodic exhaust to the atmosphere. The rotary air modulator or valve is comprised of a cylindrical stator, a rotor, and a shutter, each of which includes a plurality of equispaced ports, and air flow from the plenum chamber to the air cushion is modulated by passage through the stator and rotor in accordance with an intermediate shutter position; pressure exhaust is similarly controlled.

Abstract: An improved base plate for a vibratory seismic signal generator consists of a plurality of parallel T-bars welded together. The flange of every adjacent T-bar is inverted with respect to its neighbors.

Abstract: A vibratory seismic energy source capable of generating significant energy over a broad frequency band. The vibrating baseplate and associated structure are designed to have minimum weight while still retaining sufficient structural integrity to permit the use of high actuator forces. This, coupled with a large reaction mass results in the generation of significant energy levels in the earth at high frequencies.

Abstract: An air actuated seismic signal generator, commonly termed an air gun includes a cylindrical casing that is divided into a control chamber and a firing chamber by a sliding valve. The end face of the sliding valve that is exposed to the control chamber has a greater area than the end face exposed to the firing chamber. An air exhaust port is provided in the firing chamber; the exhaust port may be opened or closed by sliding the valve away from or towards a seat that is associated with the exhaust port. Air is admitted to the control chamber at a relatively low pressure of about 500 psi, and holds the valve in the exhaust-port-closed position because of the differential forces on the valve end faces. The firing chamber is pressurized to a relatively high pressure of about 5000 psi by a separate air supply. There is no air communication or equalization between control and firing chambers.

Abstract: A seismic land source for transmitting powerful seismic energy impulses into the earth comprising a dome-shaped bell within which is contained a substantially incompressible liquid and an air gun which can be fired for abruptly releasing pressurized gas into the liquid in the bell. A metal pan is positioned below the rim of the bell for engaging the surface of the earth below the bell and is mounted for downward movement with respect to the bell. A flexible elastomeric diaphragm extends across the bottom of the bell above the metal pan and extends upwardly beyond the bell rim between the rim and the pan. The diaphragm has a rounded shoulder portion with an upturned peripheral side wall portion extending upwardly around the exterior of the bell to an elevated level substantially above the bell rim, and the upper edge of the peripheral side wall of the diaphragm is clamped at said elevated level to a flange fixed to the outer surface of the bell.

Abstract: A method and apparatus for controlling the firing of a seismic source, wherein the firing circuit is coupled to the source by a two-conductor cable whose impedence is changed upon firing of the source. The change in cable impedence is detected and the time delay between the firing command signal and the detected change is used to control the firing command signal in order that a plurality of sources may be fired in a desired sequence.

Abstract: This device comprises two movable elements of rigid material tightly interconnected by means of a deformable membrane forming therewith a tight internal enclosure, means for varying abruptly the volume of said enclosure by successively moving the two elements away from each other, maintaining them in spaced relationship and allowing them to be urged toward each other by the effect of the external hydrostatic pressure, in which the means for moving the two elements away from each other includes two cylinders and at least one piston slidable in one of said cylinders, associated to one of said movable elements and also to a push-member slidable in one of the cylinders and bearing on the other movable element and means for feeding said cylinder with pressurized fluid so as to maintain the elements in spaced relationship or to release them.

Abstract: The gas detonator is especially adapted for shallow, seismographic, land prospecting. It comprises a circular bottom plate having an inwardly-directed sloping side wall. An annular top plate is mounted over the bottom plate. Means, including a plurality of springs, interconnect and resiliently maintain the plates in touching relation with each other. A housing is mounted over the top plate and forms therewith a detonation chamber. The bore of the top plate serves as the vent port for the detonation chamber. The vent port is normally closed by the bottom plate. Following the detonation of a combustible gas mixture in the chamber, the plates momentarily separate and form therebetween a cylindrical cavity which opens the vent port. A container upwardly extends from and forms with the bottom plate a reservoir which, in use, is filled with water. The spent gases of combustion escape into this water, thereby muffling the sound of the detonator.

Abstract: A seismic signal is generated having a pattern which is periodically repetitive. The signal within each period has a nonrepetitive pattern and each period has a time duration not less than the time required for the seismic wave to travel to the deepest subsurface strata of interest and back to the detecting location.

Abstract: Improvement in electro-fluid vibrator means used for generating seismic waves in the earth in which the flow of pressurized fluid to the vibrator is controlled in accordance with the resultant holddown pressure on the baseplate in contact with the earth, so that there is always a positive pressure on the baseplate, preventing it from being lifted off the surface of the earth. Force measuring means are provided in the holddown means. So long as this force is large and positive (in the direction to hold the baseplate to the earth) no control is required. When this positive force becomes less than a preselected value, the pressure fluid system is controlled to reduce the maximum pressure of, or rate of flow of, pressure fluid to the vibrator. The force measuring system can conveniently utilize the compliances in the holddown system as the force measuring elements.

Abstract: Method and apparatus for carrying out vibratory seismic operations and processing seismic records, involving generating a square wave analog sweep signal for driving a vibrator, generating a square wave analog, or 1 bit digitized transmitted signal, digitizing the received signal to 1 bit, and correlating the 1 bit digitized received signal with the 1 bit digitized transmitted signal, and stacking a plurality of such 1 bit correlograms. Simple logic means are disclosed for performing a 1 bit .times. 1 bit correlation. Means are disclosed for generating a square wave analog sweep signal.

Abstract: A seismic signal source apparatus is mounted on the bed of a vehicle by means of a support structure. The apparatus includes a base plate coupled to ground surface beneath the vehicle as well as a seismic signal transducer to inject sweep signals into the ground through the base plate. A restraining means is connected between the upper end of the transducer support structure and the vehicle bed to prevent rocking motion of the seismic signal source. The restraining means includes a double-acting hydraulic piston. The piston is provided with at least two spring-loaded, oppositely-directed check valves. The spring loaded valves open to allow the transducer base plate to adjust itself to the local ground contours when the transducer base plate is pressed to the ground by the weight of the vehicle. The valves remain closed during a sweep cycle to provide a rigid restraining link which prevents destructive rocking movements of the transducer and base plate during a sweep cycle.

Abstract: A seismic energy source which incorporates multiple augers and a rotary mechanism therefor mounted on a vehicle, the auger incorporating an internally situated seismic shock wave source which creates shock waves passing through a window in the auger into the soil. The shock wave source incorporates a chamber which stores compressed air and a valve mechanism which releases the air sharply for a short interval to create a shock wave in the soil.

Abstract: An apparatus for generating a series of seismic acoustic pulses in a body of water. The series is characterized by having continuously-variable, non-repetitive time intervals between successive pulses during a continuous seismic recording. The preferred generator is an air gun comprising a variable-speed motor with a rotating cam for actuating a sleeve valve which alternately opens and closes exhaust ports in a high-pressure chamber. As the valve repeatedly opens, jets of high-pressure air are impulsively expelled into the surrounding water, thereby generating an underwater acoustic pulse train.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. The synchronization and timing is achieved by controlling and monitoring the movement of the shuttle in the air gun. Various sensors are used such as an electrical coil having a constant current flowing therein which produces a flux pattern which is modified when the shuttle is accelerated, thereby inducing a voltage in said coil which is processed by appropriate processing circuitry. Another embodiment employs a magnetic sensor which includes a permanent magnet and coil wrapped therearound; the permanent magnet produces a flux pattern which is altered when the shuttle is accelerated and comes into proximity to the sensing end of said permanent magnet, thereby inducing a voltage in the coil which is then processed in appropriate processing circuitry.

Abstract: 1. An apparatus for producing low frequency compressional waves under water hich comprises two circular plates spaced in opposed parallel relation, a plurality of reciprocating fluid motors arranged in parallel between said plates, an independent fluid pump hydraulically connected to each of said motors for driving the same, a by-pass valve for each motor adjustable to vary the length of the stroke of such motor, a prime mover coupled to drive all of the pumps in synchronism, whereby the motors connected thereto reciprocate in unison to move said plates toward and away from each other at a frequency corresponding to the speed of the prime mover, and means for adjusting all of the by-pass valves in assembly, whereby the amplitude of oscillation of said plates is correspondingly varied.

Abstract: A shear wave vibrator is constructed having a frame with first and second oppositely facing plenum chambers secured to the frame and each having an outer periphery. A skirt is attached to each of the outer peripheries. A fan is attached to the frame with conduits supplying a volume of air under pressure to each of the plenum chambers. A modulation apparatus is mounted in each of the first and second plenum chambers to cause a variation in air pressure in each of the plenum chambers in accordance with a predetermined signal in a manner to cause the air pressure in one chamber to decrease at the same instant the air pressure in the oppositely facing chamber is increasing and vice versa. The entire apparatus is mounted between opposite walls of a trench.

Abstract: A method for generating and detecting seismic shear wave energy in the earth are disclosed useful for determining shear wave velocities in localized regions in the earth at sites where foundations of large civil engineering structures are proposed or earth embankments and dams have been built, thereby providing information affecting the basic dynamic design parameters for constructing or evaluating the project and obtaining earthquake resistant design. An airgun of elongated generally cylindrical configuration and having a single discharge port opening out radially on one side only for abruptly releasing compressed air in a direction perpendicular to the axis of the airgun is lowered into a borehole in a manner and by apparatus to control the direction in azimuth at which this single lateral discharge port is aimed.

Abstract: An apparatus and method for generating seismic signals are described using a modulated vacuum within a chamber plus a compliant, vibration-isolating means. This compliant, vibration-isolating means provides a seal between the chamber and the earth, and also generally prevents the vibration of the chamber from being transferred to the earth. The seismic signal is transmitted directly to the earth by the changes in absolute air pressure within the chamber (the modulated vacuum). As the vibrations of the chamber are generally out of phase with the force developed by the changes in chamber pressure, the chamber vibrations must, for good efficiency, be isolated from the earth. This arrangement is lightweight and inexpensive, as there is no need for either a special mass to induce the vibrations or a special mass to hold the vibrating mass in contact with the earth's surface.

Abstract: A sound imploder having as its exclusive function the creation of sonic phenomena when embedded in snow or ice fields. Special components are provided for production of steam as the source of the sound and heat for causing the device to immerse itself due to its own weight below the surface of the snow. A secondary sound source, in addition to the primary source, is also provided for mineral and other explorations underneath the body of snow.

Abstract: In a variable frequency seismic vibrator including an earth coupling plate, means for generating a reaction impedance, and an energy source for generating reciprocating movement of the coupling plate relative to the reaction impedance, the reaction impedance is generated by a reaction mass and a spring of variable stiffness which couples the reaction mass to the vibrator. As the frequency of vibration changes, the stiffness of the spring is automatically adjusted so that the impedance of the spring resonates with the impedance of the mass to maximize the reaction impedance, thereby increasing the operating efficiency of the vibrator.

Abstract: A device for generating sound waves for use in shallow terristrial seismology incorporates a percussion mass, a motor for driving the percussion mass to strike the ground for intermittent contact and adjustable to vary the frequency of impact, and a sensing element to provide a signal indicative of at least the instant of impact and preferably also the deceleration amplitude of impact.

Abstract: A mobile seismic energy source is formed by an automotive vehicle equipped with a vibrator type seismic energy source, a lifting mechanism, means for generating fluid pressure, and control means. Frame means pivotably linked to the vehicle chassis are provided for supporting the vibrator which is lowered into operational position and raised therefrom by the lifting mechanism acting between the vehicle chassis and linking arms of the frame means.

Abstract: A seismic signal source adaptable for use with various types of seismic exploration vehicles which move over land. A signal means forms a seismic signal, and a transfer means transfers the signal to a fluid-filled tire of the vehicle for improved and more efficient coupling of the signal to the ground surface. Whether the vehicle with which the source is mounted is stationary or moving, signals may be sent from the source into the ground.

Abstract: Improved pressurized gas discharging apparatus for use as a down-bore seismic impulse source provides a compact, efficient axially stacked assembly of components within a one piece elongated tubular shell housing having removable end closures. Within the tubular housing, removable partition means define a charge chamber and an operating chamber having an operating shuttle release means therebetween for sudden release of high pressure gas present in the charge chamber through a discharge port into the surrounding environment. Gas flow passageways for the supply of high pressure gas to the chambers extend longitudinally within the wall of the tubular housing and communicate with passages in the partition means. The shuttle release means may be actuated by a solenoid valve also removably positioned within the tubular housing for controlling gas flow through passageways also located within the walls of the tubular housing and within the partition means.

Abstract: Device for generating acoustic waves in a fluid medium by implosion, comprising a main cylinder, a main piston slidably mounted thereinto, said piston having a hollow cylindrical portion housing another cylinder solid with the main one and, through the bottom of which passes the hollow rod of another piston, actuated by hydraulic means and which drives in translation the main piston. By means of an annular valve, solid with the main piston, and further hydraulic means, the main piston may be locked in a position of spaced relationship with respect to the main cylinder and abruptly unlocked, thereby generating an implosion.

Abstract: A gas exploder for injecting seismic signals into the earth is provided with a high speed hydraulic catching apparatus which allows the exploder to rebound essentially unrestrained after it is fired at the surface and replaces it on the ground in one second or less without generating a significant false signal. The exploder falls freely from its maximum rebound height to within a few inches of the ground and is then lowered slowly to its starting position. Means are provided for automatically adjusting the position of the exploder after each shot so that it rests on the earth ready for the next firing even though compaction of the earth has taken place.

Abstract: A method for determining the precise position of the drill bit on the bottom of a long drill string in a deep borehole in the earth during a drilling operation, with a minimum of effort and interruption of the drilling process. It provides placing a plurality of geophones in an array on the surface of the earth above the expected position of the drill bit. A frangible object is inserted into the drill pipe near the surface whereby the mud stream will carry it down through the pipe to the bit where it will close off the mud flow through the bit. The mud pressure above the object will increase and when it reaches a high enough value the object will shatter and there will be a sudden flow of mud through the openings of the bit in the form of a shock wave, which will generate a seismic wave in the earth at the location of the bit. The expanding seismic wave will be detected by the geophones at the surface from which the times of arrival at the various geophones can be determined.

Abstract: A method and apparatus for determining the position of the bottom end of a long pipe in a deep water-filled borehole, comprising generating a shock wave in the water at the surface end of the pipe, timing the travel of the shock wave down the pipe to the bottom end thereof, where the shock wave will pass into the liquid in the borehole, generating an expanding seismic wave in the earth. Setting out a plurality of geophones on the earth at the surface to detect the arrival of the seismic wave. Recording the geophone signals and determining the arrival times of the seismic wave. Determining the travel times of the seismic wave to each geophone and determining the position of the end of the pipe.

Abstract: Method and apparatus for logging the position of a deep borehole filled with liquid in the earth, comprising a long, continuous small diameter pipe adapted to be reeled up on a drum mounted on a vehicle, and means to insert the end of the pipe into the mouth of a borehole and to lower it to any desired depth in the earth. A plurality of geophones are positioned on the surface of the earth in the vicinity of the borehole with conventional amplifying and recording means connected thereto. Means are provided on the vehicle for compressing a liquid or gas, and injecting it into the pipe. On the bottom end of the pipe is a chamber in which this pressurized fluid can be stored. Fast acting valve means are provided which on signal can suddenly open and permit the stored fluid in the chamber to explosively expand into the liquid in the annulus of the borehole.

Abstract: This abstract describes vibrator systems for generating elastic waves in the earth, in which an actuator has a mechanical output drive means responsive to an electrical oscillatory signal, the drive means operates a variable volume compartiment filled with fluid, which is connected by conduit to a least one vibrator, comprising an expandable closed chamber connected between a base plate and a reaction mass. Two or more compartments can be used with two or more actuator drive means, the compartments connected separately to a plurality of vibrators. The vibrators may operate in-phase on in phase opposition. The plurality of vibrators may operate in horizontal and/or vertical arrays.